1. Field of the Invention
The invention relates in general to solid deposition modeling, and in particular to a method and apparatus for providing ventilation and cooling to make solid deposition modeling with curable materials viable in an office environment.
2. Description of the Prior Art
Recently, several new technologies have been developed for the rapid creation of models, prototypes, and parts for limited run manufacturing. These new technologies are generally called Solid Freeform Fabrication techniques, and are herein referred to as “SFF.” Some SFF techniques include stereolithography, selective deposition modeling, laminated object manufacturing, selective phase area deposition, multi-phase jet solidification, ballistic particle manufacturing, fused deposition modeling, particle deposition, laser sintering, and the like. Generally in SFF techniques, complex parts are produced from a modeling material in an additive fashion as opposed to conventional fabrication techniques, which are generally subtractive in nature.
In most SFF techniques, structures are formed in a layer by layer manner by solidifying or curing successive layers of a build material. For example, in stereolithography a tightly focused beam of energy, typically in the ultraviolet radiation band, is scanned across a layer of a liquid photopolymer resin to selectively cure the resin to form a structure. In Selective Deposition Modeling, herein referred to as “SDM,” a build material is typically jetted or dropped in discrete droplets, or extruded through a nozzle, in order to solidify on contact with a build platform or previous layer of solidified material in order to build up a three-dimensional object in a layerwise fashion. Other synonymous names for SDM which are used in this industry are solid object imaging, solid object modeling, fused deposition modeling, selective phase area deposition, multi-phase jet modeling, three-dimensional printing, thermal stereolithography, selective phase area deposition, ballistic particle manufacturing, fused deposition modeling, and the like. Ballistic particle manufacturing is disclosed in, for example, U.S. Pat. No. 5,216,616 to Masters. Fused deposition modeling is disclosed in, for example, U.S. Pat. No. 5,340,433 to Crump. Three-dimensional printing is disclosed in, for example, U.S. Pat. No. 5,204,055 to Sachs et al. Often a thermoplastic material to having a low-melting point is used as the solid modeling material in SDM; which is delivered through a jetting system such as an extruder or print head. One type of SDM process which extrudes a thermoplastic material is described in, for example, U.S. Pat. No. 5,866,058 to Batchelder et al. One type of SDM process utilizing ink jet print heads is described in, for example, U.S. Pat. No. 5,555,176 to Menhennett et al.
Recently, there has developed an interest in utilizing curable materials in SDM. One of the first suggestions of using a radiation curable build material in SDM is found in U.S. Pat. No. 5,136,515 to Helinski, wherein it is proposed to selectively dispense a UV curable build material in an SDM system. Some of the first UV curable material formulations proposed for use in SDM systems are found in Appendix A of International Patent Publication No. WO 97/11837, where three reactive material compositions are provided. More recent teachings of using curable materials in various selective deposition modeling systems are provided in U.S. Pat. No. 6,259,962 to Gothait; U.S. Pat. Nos. 6,133,355 and 5,855,836 to Leyden et al; U.S. Pat. App. Pub. No. U.S. 2002/0016386 A1; and International Publication Numbers WO 01/26023, WO 00/11092, and WO 01/68375.
These curable materials generally contain photoinitiators and photopolymers which, when exposed to ultraviolet radiation (UV), begin to cross-link and solidify. As this occurs, a significant amount of exothermic heat is produced, which must be removed from the system as objects are built. In addition, care must be taken in working with these materials as prolonged dermal contact can lead to sensitization, and their vapors can provide undesirable odors. Thus, it is important to minimize human contact with these materials when in liquid form, and to prevent these materials from becoming airborne in an office environment when in vapor form.
For SDM systems that selectively dispense curable materials, a radiation curing step is needed to initiate the curing process. However, radiation curing exposure systems themselves generate significant amounts of heat, whether they are flash systems or continuous flood systems. The high levels of heat generated by these lamps pose significant problems in SDM. For instance, the heat generated by these lamps can thermally initiate curing of the material in the SDM dispensing device or material delivery system rendering the apparatus inoperable. Being able to remove this heat in an SDM apparatus is crucial to acceptable operation of the system.
One of the advantages of first generation SDM machines that worked with thermoplastic waxes to build objects was that the machines could be used in an office environment. This is because the waxes are essentially benign in nature, requiring no need to prevent human contact. Further, power consumption and heat generation is not much more when dispensing these materials from SDM compared to other office equipment such as photocopier. However, making an SDM apparatus utilizing curable materials for use in an office environment is no trivial task. Power consumption must be kept at a minimum so as to meet conventional power requirements found in an office, such as 20 A/115V service. Heat generation must be kept low enough so that standard office air conditioning systems can maintain a comfortable office environment, and the cooling system of the SDM apparatus must be sufficient to remove the generated heat from the system. Also the ventilation system must be able to trap vapors within the apparatus and prevent their potentially odorous release into the office environment.
Thus, there is a need to develop an inexpensive ventilation and cooling system for use in an SDM apparatus capable of removing large amounts of localized heat while also preventing vapors from being released into the environment. These and other difficulties of the prior art have been overcome according to the present invention.